Changes in oxygen tension during radiotherapy of head and neck tumours

Increased knowledge about changes that occur in tumour oxygenation during radiotherapy and the biological factors causing these changes can be useful in the development of optimal radiation treatments. The aims of this study were a) to study changes in the oxygen tension (pO2) of human head and neck tumours during radiotherapy in relationship to changes in cell density and vascular density, and b) to investigate whether the pO2, measured before or during therapy, can be used to predict the therapeutic outcome. Preliminary data from the first 11 patients included in the study are reported. The pO2 was measured before treatment (11 patients) and once a week during therapy (8 patients), using polarographic needle electrodes. Cell density and vascular density were determined from biopsies taken after each pO2 measurement in 5 patients. Significant fluctuations in pO2 occurred during therapy. Changes in hypoxic fraction; i.e., fraction of pO2 readings below 2.5 mm Hg, 5 mm Hg or 10 mm Hg, coincided with changes in cell density, but not with changes in vascular density, which suggests that the changes in hypoxic fraction were caused by changes in oxygen consumption rather than supply. Response evaluation after a median follow-up time of 19 months showed that progressive disease occurred among the patients with highly hypoxic tumour, regardless of whether hypoxic fraction before treatment or after two weeks of radiotherapy was considered.     

Tumor oxygenation after radiotherapy, chemotherapy, and/or hyperthermia predicts tumor free survival

PURPOSE: To investigate the influence of different treatment modalities (radiotherapy, chemotherapy, and hyperthermia) on the oxygenation of human tumor xenografts and to correlate it with the tumoricidal effect we conducted this study. METHODS AND MATERIALS: Human-derived head-and-neck squamous cell carcinoma xenografts (implanted in nude mice/nine groups of 10 mice) were treated with various treatment modalities and combinations of them (radiation with 5 x 2 or 10 x 2 Gy, hyperthermia at 41 degrees C or 41.8 degrees C, chemotherapy with ifosfamide [32 mg/kg] or cisplatin [2 mg/kg]). The tumor volume was evaluated 3 times per week until Day 60. Tumor pO(2) was measured at Day 1, 5, 8, and 12 with a polarographic pO(2) histograph. RESULTS: Within treatment time (maximum, 10 days) the median pO(2) increased in all groups (except the control group), concomitantly the fraction of measurements of pO(2) that were less than 10 mm Hg showed a constant decrease (p < or = 0.001). The highest difference between the median pO(2) values and the fraction of measurements of pO(2) that were less than 10 mm Hg at the start and 1 week after the end of therapy occurred in the groups with radiochemothermotherapy (triple-modality therapy; p< or = 0.001). At Day 60, the highest rate of complete remissions was observed in the triple-modality therapy groups. CONCLUSION: Tumor oxygenation under a single or combined cancer treatment is correlated with treatment efficacy in terms of complete remissions at Day 60. The posttherapeutic fraction of measurements of pO(2) that were less than 10 mm Hg correlates even better with the long term tumor free survival than the median pO(2) values or the pretherapeutic fraction of measurements of pO(2) that were less than 10 mm Hg.     

Changes in oxygenation during radiotherapy in carcinoma of the cervix.

PURPOSE: The aim of this study was to investigate changes in tumor oxygenation, assessed by polarographic needle electrode measurements, following fractionated external beam radiotherapy in carcinoma of the cervix. METHODS AND MATERIALS: Normal and tumor tissue oxygenation was measured in 19 patients prior to radiotherapy and after 40-45 Gy of external beam radiotherapy delivered in 20 fractions over 4 weeks. All measurements were performed during anesthesia. RESULTS: There was no significant difference in the level of normal tissue oxygenation pre- and post radiotherapy. The individual patient median tumor pO2 values ranged from 0 to 31 mmHg pre-radiotherapy and 1 to 61 mmHg post-radiotherapy. The mean of the 19 median pO2 values increased from 8 (SD +/- 10) mmHg to 20 (+/- 20) mmHg following external beam radiotherapy. The increase was significant by paired Wilcoxon test (p = 0.011). There was also a significant fall in the proportion of values < 5 mmHg (p = 0.040). Although this value remained constant, or fell, in the majority of patients (15/19), it increased in 4 tumors. Tumor size pre- and postradiotherapy did not correlate with the level of pretreatment oxygenation; neither did the change in tumor size and change in level of oxygenation. CONCLUSION: The level of tumor oxygenation increased in the majority of patients (15/19) following 40-45 Gy of radiotherapy in carcinoma of the cervix.     

Effects of texaphyrins on the oxygenation of EMT6 mouse mammary tumors

PURPOSE: To investigate the effects of texaphyrins on the oxygenation of EMT6 mouse mammary tumors in Balb/c Rw mice. Texaphyrins are synthetic, porphyrin-like molecules capable of stably coordinating lanthanide and nonlanthanide metals. Metallotexaphyrin compounds containing gadolinium (MGd), lutetium (MLu), europium (Eu-Tex), dysprosium (Dy-Tex), and manganese (Mn-Tex) were evaluated. METHODS: Tumor oxygenation was measured using an Eppendorf pO2 histograph when tumors, implanted intradermally in the rear dorsum, reached 150-200 mm3. Oxygen measurements were also made in the leg muscle of tumor-bearing mice, to determine whether changes in oxygenation occurred in nontumor tissue. RESULTS: Motexafin gadolinium (Xcytrin, MGd) seems to be an effective modulator of tumor oxygen tension. The mean of the median tumor pO2 6 hours after injection of MGd was 8.0 +/- 2.4 mm Hg. The control value was 1.5 +/- 0.4 mm Hg. The oxygen levels within EMT6 tumors were shifted significantly toward higher oxygen tensions 6-8 hours after i.v. injection of 40 micromol/kg MGd, thereby reducing the percentage of severely hypoxic readings (MGd, 6 hours: 44.6 +/- 4.3% <2.5 mm Hg; Control: 69.4 +/- 3.0% <2.5 mm Hg). There was no significant change in the oxygenation of the leg muscle after MGd treatment. Eu-Tex and Mn-Tex increased the tumor oxygenation to a much lesser degree than MGd. MLu, Dy-Tex, and the vehicle (a 5% mannitol solution) did not modulate tumor oxygenation. CONCLUSIONS: MGd is an effective modulator of tumor oxygenation. The central metal composition of texaphyrin compounds is an important determinant of the effect of the texaphyrins on tumor oxygenation.     

Oxygenation of carcinomas of the uterine cervix: evaluation by computerized O2 tension measurements

Direct oxygen partial pressure (pO2) readings in cancers of the cervix and in the normal cervix of nulliparous or parous women were obtained using a computerized pO2 histography system. The oxygenation status of the tumors was evaluated as a function of clinical staging and histological grading. pO2 measurements were performed with a customized electrode system in conscious pre- and postmenopausal, untreated patients with well-defined arterial blood gas status. With this technique, pO2 measurements in the normal cervix of nulliparous women resulted in oxygenation patterns which were characteristic for normal, adequately supplied tissues (median pO2, 48 mm Hg) with approximately 1% of the pO2 values grouped between zero and 2.5 mm Hg, i.e., in a range with less than half-maximum radiosensitivity. As a rule, the mean (and median) pO2 values were distinctly lower in the normal cervix of parous women (most probably due to scar formation following vaginal delivery) and in malignancies. In the normal cervix of parous women the median pO2 value was 13 mm Hg (with approximately 14% of the pO2 readings in the lowest class), 14 mm Hg in International Federation of Gynecologists and Obstetricians I/II tumors (2% of the readings in the lowest pO2 class), and 11 mm Hg in International Federation of Gynecologists and Obstetricians III/IV cancers (1% of the pO2 data in the lowest class). To date, 5 of 18 cervical cancers exhibited pO2 values between zero and 2.5 mm Hg. The oxygenation pattern in cervical cancers and the occurrence of hypoxia and/or anoxia did not correlate with either the clinical stages and histological grades or with a series of clinically relevant parameters (e.g., tumor size). No significant differences were found between pre- and postmenopausal tumors, between squamous cell carcinomas and adenocarcinomas, and between endophytic or exophytic tumors. From these studies there is clear indication that the oxygenation status of individual tumors cannot be predicted on the basis of staging and/or grading, predominantly because of the pronounced tumor-to-tumor variabilities. Evaluation of the tissue oxygenation of individual tumors is thus mandatory to prove that tumor oxygenation can predict the overall prognosis and/or treatment outcome.     

Oxygenation of head and neck cancer: changes during radiotherapy and impact on treatment outcome.

BACKGROUND AND PURPOSE: To evaluate the long term clinical significance of tumor oxygenation in a population of head and neck cancer patients receiving radiotherapy and to assess changes in tumor oxygenation during the course of treatment. METHODS AND MATERIALS: Patients with head and neck cancer receiving primary RT underwent pretreatment polarographic tumor oxygen measurement of the primary site or a metastatic neck lymph node. Treatment consisted of once daily (2 Gy/fraction to a total dose of 66-70 Gy) or twice daily irradiation (1.25 Gy/fraction to 70-75 Gy) to the primary site. Twenty-seven patients underwent a second series of measurements early in the course of irradiation. RESULTS: Sixty-three patients underwent pretreatment tumor oxygen assessment (primary site, n = 24; nodes, n = 39). The median pO2 for primary lesions was 4.8 mmHg, and it was 4.3 mmHg for cervical nodes. There was a weak association between anemia and more poorly oxygened tumors, but many non-anemic patients still had poorly oxygenated tumors. Repeat assessments of tumor oxygenation after 10-15 Gy were unchanged compared to pretreatment baselines. Poorly oxygenated nodes pretreatment were more likely to contain viable residual disease at post-radiation neck dissection. Median follow-up time for surviving patients was 20 months (range 3-50 months). Hypoxia (tumor median pO2 <10 mmHg) adversely affected 2 year local-regional control (30 vs. 73%, P = 0.01), disease-free survival (26 vs. 73%, P = 0.005), and survival (35 vs. 83%, P = 0.02). CONCLUSION: Tumor oxygenation affects the prognosis of head and neck cancer independently of other known prognostic variables. This parameter may be a useful tool for the selection of patients for investigational treatment strategies.     

Temperature-dependent changes in physiologic parameters of spontaneous canine soft tissue sarcomas after combined radiotherapy and hyperthermia treatment

PURPOSE: The objectives of this study were to evaluate effects of hyperthermia on tumor oxygenation, extracellular pH (pHe), and blood flow in 13 dogs with spontaneous soft tissue sarcomas prior to and after local hyperthermia. METHODS AND MATERIALS: Tumor pO2 was measured using an Eppendorf polarographic device, pHe using interstitial electrodes, and blood flow using contrast-enhanced magnetic resonance imaging (MRI). RESULTS: There was an overall improvement in tumor oxygenation observed as an increase in median pO2 and decrease in hypoxic fraction (% of pO2 measurements <5 mm Hg) at 24-h post hyperthermia. These changes were most pronounced when the median temperature (T50) during hyperthermia treatment was less than 44 degrees C. Tumors with T50 > 44 degrees C were characterized by a decrease in median PO2 and an increase in hypoxic fraction. Similar thermal dose-related changes were observed in tumor perfusion. Perfusion was significantly higher after hyperthermia. Increases in perfusion were most evident in tumors with T50 < 44 degrees C. With T50 > 44 degrees C, there was no change in perfusion after hyperthermia. On average, pHe values declined in all animals after hyperthermia, with the greatest reduction seen for larger T50 values. CONCLUSION: This study suggests that hyperthermia has biphasic effects on tumor physiologic parameters. Lower temperatures tend to favor improved perfusion and oxygenation, whereas higher temperatures are more likely to cause vascular damage, thus leading to greater hypoxia. While it has long been recognized that such effects occur in rodent tumors, this is the first report to tie such changes to temperatures achieved during hyperthermia in the clinical setting. Furthermore, it suggests that the thermal threshold for vascular damage is higher in spontaneous tumors than in more rapidly growing rodent tumors.     

A pilot study comparing intratumoral oxygenation using the comet assay following 2.5% and 5% carbogen and 100% oxygen

PURPOSE: Tumor hypoxia has been purported to be an important biologic factor in the failure of radical radiotherapy to achieve local control in many tumor types. This study was designed to evaluate the effect of breathing high oxygen content gas mixtures (oxygen with 0%, 2.5%, or 5% carbon dioxide) on tumor oxygenation measured using the Eppendorf polarographic oxygen electrode and the comet assay in accessible, hypoxic human tumors. METHODS AND MATERIALS: Using Eppendorf pO2 histography to identify hypoxic tumors (median pO2 < or = 10 mmHg), eligible patients were systematically allocated either 100% oxygen (O2) or oxygen with 2.5% or 5% carbon dioxide (CO2). Tumors were treated with 6-10 Gy during which two fine needle aspirates (FNA) were obtained from different regions of the lesion, one at midway and the other at completion of the radiation exposure. Gas breathing was initiated 4 min before radiation was commenced. A 10-min interval was specified between the first and second halves of the radiation exposure to allow near maximal DNA repair prior to the second half of the radiation treatment. FNAs were performed within 2 min of cessation of radiation and the cells immediately suspended in buffered saline at 4 degrees C for analyses of hypoxic fraction using the comet assay. RESULTS: Fifteen evaluations were performed in 13 patients with hypoxic tumors (median O2 tension 2.75 mmHg) treated with a median dose of 8 Gy. The median hypoxic fraction determined using the comet assay fell from 0.36 to 0.13 (p = 0.001, Wilcoxon signed rank test) due to the addition of high oxygen content gases. CONCLUSIONS: In tumors defined as hypoxic using Eppendorf pO2 histography, a statistically significant reduction in the hypoxic fraction with the comet assay was found following administration of high oxygen content gases. These preliminary findings reveal a trend suggesting that 5% carbogen may reduce the hypoxic fraction by a greater margin than either 100% oxygen or 2.5% carbogen.     

Oxygenation of human tumors: evaluation of tissue oxygen distribution in breast cancers by computerized O2 tension measurements

Direct oxygen partial pressure (pO2) readings in breast cancers, in fibrocystic disease, and in the normal breast have been obtained using a novel technique which allows for the systematic evaluation of the oxygenation status as a function of pathological staging and histological grading. Measurements were performed in awake pre- and postmenopausal patients with well-defined arterial blood gas status. The measuring procedure encompasses a computerized electrode movement in the tissue which avoids significant compression artifacts and allows routine measurement in human tumors before, during, and after treatment. Using this reliable technique, pO2 measurements in the normal breast and in fibrocystic disease resulted in oxygenation patterns which were characteristic for normal, adequately supplied tissues. The median pO2 values were 65 and 67 mm Hg, respectively, with no pO2 readings below 12.5 mm Hg in the normal breast, and less than or equal to 5 mm Hg in fibrocystic disease, respectively. In contrast, in breast cancers the median pO2 value was 30 mm Hg (pooled data for pathological stages T1-T4). To date, 6 of 15 breast cancers exhibited pO2 values between zero and 2.5 mm Hg, i.e., tissue areas with less than half-maximum radiosensitivity. The oxygenation pattern in breast cancers and the occurrence of hypoxia and/or anoxia did not correlate with either the pathological stages and histological grades or with a series of clinically relevant parameters. No significant differences were found between pre- and postmenopausal tumors and between lobular and ductal carcinomas. Tumor-to-tumor variability in the oxygenation pattern was more pronounced than intra-tumor heterogeneity. pO2 variations within a tumor cannot be predicted, e.g., as a function of the measuring site (tumor center versus periphery).     

Anemia in cervical cancers: impact on survival,patterns of relapse,and association with hypoxia and angiogenesis

PURPOSE: The prognostic impact of anemia in cervical cancers is well established. We have investigated the impact of anemia on prognosis and patterns of relapse in cervical cancers. Furthermore, we analyzed the relationship between anemia, tumor hypoxia, and angiogenesis. METHODS AND MATERIALS: Eighty-seven patients (mean age 58 years) with squamous cell cancer of the cervix (Stage IIB: n = 19; Stage IIIB: n = 59; Stage IVA: n = 9) were prospectively enrolled in the study from 1995 through 1999. Patients underwent definitive radiotherapy with a combination of external beam radiotherapy (45-50.4 Gy) and high-dose-rate brachytherapy (5 x 7 Gy). Tumor oxygenation was measured with the Eppendorf pO(2)-histograph before radiotherapy and after 19.8 Gy. Angiogenesis was determined by measuring the microvessel density in pretreatment biopsies in 46 patients. The impact of tumor oxygenation (at 0 Gy and 19.8 Gy), hemoglobin (hb) level (at 0 Gy and 19.8 Gy), angiogenesis and clinical parameters on survival and relapse was investigated. RESULTS: The 3-year overall survival rate (after a median follow-up of 42 months) was 57% for the whole group of patients, 72% for Stage IIB, 60% for Stage IIIB, and 22% for Stage IVA. The presence of pretreatment anemia had a significant impact on the relapse rate. However, the midtherapy hb level (at 19.8 Gy) had the strongest impact on local failure rate and survival: 3-year local failure rate was 6% in 20 patients with a hb > 13 g/dL at 19.8 Gy, 15% in 47 patients with an hb between 11 and 13 g/dL, and 67% in 20 patients with an hb < 11 g/dL, p = 0.0001. This was associated with a significant impact on the 3-year overall survival, 79% vs. 64% vs. 32%. Twenty-three tumors were poorly oxygenated at both measurements (oxygen pressure [median pO(2)] < 15 mm Hg before therapy and at 19.8 Gy). This group had a significantly lower 3-year overall survival as compared with patients with high pO(2) before and/or at 19.8 Gy (38% vs. 68%, p = 0.02), and these poorly oxygenated tumors had also a significantly increased microvessel density. In a multivariate model, the midtherapy hb level maintained an overwhelming impact on local failure rate and survival. CONCLUSION: Hemoglobin level during radiotherapy was the strongest prognostic factor for local control and survival. We could further identify a poor prognostic subgroup with persisting hypoxia during radiotherapy, low hb levels, and increased angiogenesis. According to these findings, an association between anemia, poor tumor oxygenation, and angiogenesis is likely.     

Androgen withdrawal in patients reduces prostate cancer hypoxia: implications for disease progression and radiation response

Hypoxia is a feature of many human malignancies, and leads to aggressive clinical behavior and recurrence after treatment. Here, we show for the first time that androgen withdrawal reduces prostate cancer hypoxia in patients. Oxygen measurements were done in 248 patients with clinically localized prostate cancer prior to radiotherapy, and showed hypoxia of potential biological and clinical significance. In 22 of these patients, prostate oxygen levels were measured both before and after 30 to 145 days of the androgen antagonist bicalutamide. There was a significant reduction in tumor hypoxia with androgen withdrawal (P=0.005). The median pO(2) increased from 6.4 to 15 mm Hg, and the hypoxic proportion decreased from 40% to 31%. However, the response was heterogeneous, with improvement in 12 patients, stable oxygen readings in 9 patients and worsening hypoxia in 1 patient. Among the responding patients, the median pO(2) increased from 4.9 to 33 mm Hg, and the hypoxic proportion decreased from 51% to 23%. There was no apparent relationship between the change in oxygenation and baseline prostatic volume, T category, Gleason score, prostate-specific antigen levels, the duration of treatment with bicalutamide, or the change in prostate-specific antigen levels with bicalutamide. These results might, in part, explain the improved patient outcome that has been observed in clinical trials of radiotherapy and hormones, and suggest a role for novel therapeutic agents that block the molecular response to hypoxia in prostate cancer either alone or in combination with other established treatments.     

Photodynamic therapy with verteporfin in the radiation-induced fibrosarcoma-1 tumor causes enhanced radiation sensitivity

Photodynamic therapy (PDT) with verteporfin (lipid form of benzoporphyrin derivative,benzoporphyrin derivative monoacid ring A) was used to treat radiation-induced fibrosarcoma tumors before X-ray treatment. When verteporfin was injected 3 h before light irradiation, the tumor partial pressure of oxygen (pO(2)) rose from a pretreatment value of 2.8 +/- 1 to 15.2 +/- 6.9 mm Hg immediately after light application was complete (P = 0.048). When the optical irradiation was given 15 min after verteporfin injection, the tumor pO(2) decreased slightly after treatment [i.e., 6.8 +/- 1.6 mm Hg (pretreatment) versus 4.1 +/- 0.3 mm Hg (posttreatment)], whereas control tumor pO(2) did not change significantly. In vitro study of the cellular oxygen consumption rate before and after PDT treatment indicated that the consumption rate decreased linearly with delivered optical dose and quantitatively matched the loss of cell viability as measured by a mitochondrial tetrazolium assay. Doppler measurements show that red cell flux is still patent immediately after treatment, indicating that oxygen should still be delivered to the tumor. Computational simulations of the oxygen supply from the vessels and the consumption from mitochondrial activity confirmed that if oxygen consumption is decreased in the presence of unhindered blood flow, the tumor oxygenation should rise, and the hypoxic fraction of the tumor should decrease. Combination treatments with PDT delivered (100 J/cm(2) optical dose, with 1 mg/kg benzoporphyrin derivative monoacid ring A injected 3 h before treatment) after radiation treatment (10 Gy from 300 keV source) were compared with PDT delivered simultaneously with radiation. Tumor regrowth assay showed that the delays to reach double the tumor volume for PDT alone and radiation alone were 2.7 +/- 1.6 and 3.2 +/- 1.7 days, respectively. When radiation was given before PDT, the delay was 5.4 +/- 1.4 days, and when PDT was given at the same time as radiation, the delay was 8.1 +/- 1.5 days. This observation indicates that the combined effect in the latter case was greater than additive (P = 0.049).     

Tumor hypoxia--a confounding or exploitable factor in interstitial brachytherapy? Effects of tissue trauma in an experimental rat tumor model

PURPOSE: To evaluate the potential effects of tumor hypoxia induced by afterloading catheter implantation on the effectiveness of brachytherapy in a rat tumor model. METHODS AND MATERIALS: Afterloading catheters (4) were implanted in subcutaneously growing R1M rhabdomyosarcoma in female Wag/Rij rats. A MicroSelectron (Nucletron) was used for interstitial high-dose-rate irradiation ((192)Ir). Tumor oxygenation, perfusion, and cell survival were assessed by pO(2) histography (Eppendorf), Tc-99m injection, and excision assay, respectively. RESULTS: Tumor perfusion was markedly reduced at 1 h after catheter implantation (33.9 +/- 6.0% (SEM, n = 9) of control) and partly recovered after 5 h (61.5 +/- 12.2%). At 24 h, the perfusion level reached control values (100.6 +/- 25.7%), but was highly variable with some of the tumors showing hardly any recovery at all. Tumor oxygenation showed a similar pattern, but with less recovery. Median pO(2) readings were 13.5, 1.2, and 5.3 mm Hg before and at 1 and 24 h after implantation, respectively (7 tumors). The percentages of pO(2) readings 相似文献   

Increasing levels of hypoxia in prostate carcinoma correlate significantly with increasing clinical stage and patient age: an Eppendorf pO(2) study

BACKGROUND: The purpose of this study was to analyze the extent of hypoxia in prostate carcinoma tumors using the Eppendorf pO(2) microelectrode and correlate this with pretreatment characteristics and prognostic factors. METHODS: Custom-made Eppendorf pO(2) microelectrodes were used to obtain pO(2) measurements from the pathologically involved region of the prostate (as determined by the pretreatment sextant biopsies) as well as from a region of normal muscle for comparison. Each set of measurements comprised approximately 100 separate readings of pO(2), for a total of 10,804 individual measurements. Fifty-five patients with localized prostate carcinoma were studied: Forty-one patients received brachytherapy implants, and 14 patients underwent radical prostatectomy. The pO(2) measurements were obtained in the operating room by using a sterile technique under spinal anesthesia for the brachytherapy group and under general anesthesia for the surgery group. The Eppendorf histograms were recorded and described by the median pO(2), mean pO(2), and percentage < 5 mm Hg and < 10 mm Hg. A multivariate mixed-effects analysis for the prediction of tumor oxygenation was performed and included the following covariates: type of tissue (prostate vs. muscle), type of treatment (implant vs. surgery) and/or anesthesia (spinal vs. general), prostate specific antigen level, disease stage, patient age and race, tumor grade, tumor volume, perineural invasion, and hormonal therapy. RESULTS: Due to differences in patient characteristics and the anesthesia employed, control measurements were obtained from normal muscle (in all but two patients). This internal comparison showed that the oxygen measurements from the pathologically involved portion of the prostate were significantly lower (average median pO(2), 9.9 mm Hg) compared with the measurements normal muscle (average median pO(2), 28.6 mm Hg; P < 0.0001). A multivariate, linear, mixed analysis demonstrated that, among all of the patients, the significant predictors of oxygenation were tissue (prostate vs. muscle) and anesthesia (spinal vs. general) or treatment (implant vs. surgery). Among the brachytherapy (spinal anesthesia) patients, the significant predictors of pO(2) were tissue type, disease stage, and patient age. There were no significant predictors of oxygenation in the surgical (general anesthesia) group. CONCLUSIONS: This study, employing in vivo electrode oxygen measurements, demonstrated that hypoxia exists in prostate carcinoma tumors. A dramatic effect of anesthesia was observed, likely due to modulation of polarography in the presence of fluorine. Within the group of brachytherapy (spinal anesthesia) patients, increasing levels of hypoxia (within prostatic tissue) correlated significantly with increasing clinical stage and patient age. More patients will be accrued to this prospective study to further correlate the oxygenation status in prostate carcinoma tumors with known prognostic factors and, ultimately, treatment outcome.     

Correlation of radiation response with tumor oxygenation in the Dunning prostate R3327-AT1 tumor

PURPOSE: To investigate the application of pretreatment oxygenation to the AT1 subline of the Dunning R3327 prostate tumor, which is more hypoxic and faster growing than the H1 subline previously studied. METHODS AND MATERIALS: Dunning prostate R3327-AT1 tumors growing on Copenhagen rats were administered 30 Gy of X-ray radiation either with or without oxygen inhalation. Tumor oxygenation was sampled by (19)F nuclear magnetic resonance echo planar imaging relaxometry of the reporter molecule hexafluorobenzene, no more than 24 h before irradiation. RESULTS: Large tumors (>3.0 cm(3)) exhibited significantly greater hypoxic fractions and lower mean partial pressure of oxygen (pO(2)) than their smaller counterparts (<1.5 cm(3)). However, unlike the R3327-HI subline, large AT1 tumors generally did not respond to oxygen inhalation in terms of altered hypoxic fraction or response to irradiation. Although the tumors did not respond to oxygen inhalation, each tumor had a different pO(2), and there was a clear trend between level of oxygenation at time of irradiation and tumor growth delay, with considerably better outcome when mean pO(2) > 10 mm Hg. The comparatively small baseline hypoxic fraction in the group of small tumors was virtually eliminated by breathing oxygen, and the growth rate was significantly reduced for tumors on rats breathing oxygen during irradiation. CONCLUSIONS: These results further validate the usefulness of nuclear magnetic resonance oximetry as a predictor of response to radiation therapy.     

Oxygen tension measurements of tumors growing in mice.

PURPOSE: Clinical studies using the Eppendorf histograph have shown that patients whose tumors have a low pO2 have worse local control after radiotherapy, and have higher metastatic rates. Because preclinical studies of methods of overcoming, or exploiting, hypoxia generally use transplanted tumors in mice, we have compared the oxygenation of mouse tumors with human tumors to determine the appropriateness of the transplanted mouse model for such preclinical studies. METHODS AND MATERIALS: We evaluated the oxygenation status of subcutaneous (s.c.) tissue and of 12 intradermally (i.d.)- and 7 s.c.-growing mouse or human transplanted tumors in mice using the Eppendorf histograph, and compared the values obtained with measurements of human head and neck nodes. RESULTS: The normal tissue pO2 profile of air-breathing mice showed a nearly Gaussian distribution (38.2+/-14.9 mmHg). Breathing 10% O2 or carbogen resulted in dramatic changes in normal tissue oxygenation. Tumors growing intradermally in the back of air-breathing mice were extremely hypoxic and resistant to expected changes in oxygenation (carbogen breathing, size, and use of anesthetics). Tumors growing s.c. in the foot showed higher oxygen profiles with marked changes in oxygenation when exposing the animals to different levels of oxygen. However, the oxygenation of the mouse tumors transplanted in either site was only a fraction of that of the majority of human tumors. CONCLUSION: Experimental mouse tumors are markedly hypoxic, with median values of 10-20% of those of human tumors. Hence, mouse tumors are probably good models for the most hypoxic human tumors that respond poorly to radiotherapy; however, caution has to be exercised in extrapolating data from mouse to man.     

Interrelationship of proliferation and hypoxia in carcinoma of the cervix

PURPOSE: In human cervix cancer treated with radiotherapy, we have previously shown from separate groups of patients that tumor hypoxia and proliferation rate as measured by bromodeoxyuridine (BrdU) labeling index (LI) are important determinants of clinical outcome. We now examine the relationship of these two pre-treatment predictive assays in 43 patients studied prospectively from 1994-98 where both tests were performed for each patient. MATERIAL AND METHODS: Newly diagnosed patients with carcinoma of the cervix were examined under anesthesia for staging purposes. Patients were given BrdU (200 mg) by intravenous route prior to the procedure. Tumor oxygenation was measured with the Eppendorf pO2 histograph. Biopsy of tumor was then performed and the BrdU LI was obtained by flow cytometry. The degree of tumor hypoxia for each tumor was expressed as median pO2 values, and as the percentage of pO2 readings <5 mm Hg (HP5). RESULTS: The median age was 53 years (range 23-79 years). There were 32 squamous, and 11 non-squamous carcinomas. FIGO stages were: IB and IIA, 8; IIB, 17; IIIB, 18; with a median tumor size of 6 cm (range 2-10 cm). The patients received uniform treatment with radical radiation therapy. There were 22 diploid and 21 aneuploid tumors. The median LI, pO2, and HP5 were 8.0%, 5.4 mm Hg, and 46.8%, respectively. Tests for linear associations showed no significant correlation between median pO2 vs. LI (r = 0.078, p = 0.62), and HP5 vs. LI (r = -0.14, p = 0.38). CONCLUSIONS: The clinical outcome in this group of patients is immature, but these results suggest that tumor hypoxia and proliferation measurements are independent and potentially complementary predictive assays in cervix carcinoma. Further investigations are required to examine the distribution of proliferating tumor cells and its relationship with hypoxic tumor cells in tissue sections with the use of immunohistological techniques and image analysis systems.     

Disease control of uterine cervical cancer: relationships to tumor oxygen tension, vascular density, cell density, and frequency of mitosis and apoptosis measured before treatment and during radiotherapy.

Identification of biological parameters of major importance for the control of malignant diseases can be useful for the design of optimal treatment regimes for individual patients. Tumor oxygen tension (pO2), vascular density, cell density, and frequency of mitosis and apoptosis were measured before treatment (40 patients) and after 2 weeks of radiotherapy (22 patients) in patients with uterine cervical cancer. The aim was to investigate whether one of the parameters was more important for disease control than the others. Three sets of data were considered; the pretreatment parameters, the parameters measured after 2 weeks of radiation, and the changes in the parameters during this time. The pO2 was measured polarographically; the other parameters were determined by histological analyses of tumor biopsies. Hypoxic subvolume (HSV5), ie., the fraction of pO2 readings <5 mm Hg multiplied with tumor volume, showed the strongest correlation to control. Patients with a small HSVs before treatment had a higher control probability after a median follow-up time of 50 months than patients with a large HSV5 (P < 0.001). All other parameters or changes in parameters showed impaired correlation to control compared with pretreatment HSV5. The present results suggest that pretreatment oxygenation is more important for disease control of cervical cancer than the oxygenation after 2 weeks of radiotherapy or the changes in oxygenation during this time. Moreover, vascular density, cell density, and frequency of mitosis and apoptosis before treatment or after 2 weeks of therapy are probably not as important as pretreatment oxygenation as well. Although significant correlations between disease control and some of the parameters other than pretreatment oxygenation can occur in studies based on a large number of patients, the specificity of these parameters in the prediction of control is probably not as high as for oxygenation.     

Oxygenation gain factor: a novel parameter characterizing the association between hemoglobin level and the oxygenation status of breast cancers

Tumor hypoxia has been linked to acquired treatment resistance, tumor progression, and poor prognosis. Because anemia is a major causative factor for the development of hypoxia, the association between blood hemoglobin concentration (cHb) and breast cancer oxygenation was examined in this study. In addition, a novel parameter characterizing the relationship between oxygenation status and rising cHb is introduced: the oxygenation gain factor (OGF). In breast cancer patients, median cHb over the range 8.5-14.7 g/dl correlated positively with the median pO(2) (3-15 mm Hg), yielding an average OGF of 2 mm Hg.dl/g. In contrast, in normal tissues (normal breast, subcutis, and skeletal muscle) the median pO(2) values were substantially higher (52 mm Hg, 51 mm Hg, and 37 mm Hg, respectively) and remained constant irrespective of the hemoglobin level over the range from 10 to 16 g/dl (OGF = 0 in grade I anemia and nonanemic patients). Moderately lower median pO(2) values in subcutis and skeletal muscle were only observed in grade II anemia (8 g/dl < cHb < or =10 g/dl), although this would appear to be of no biological relevance. Conversely, in breast cancers, even mild anemia (grade I anemia) is a major causative factor for the development of hypoxia or anoxia.     

Polarographic electrode study of tumor oxygenation in clinically localized prostate cancer

PURPOSE: To describe the oxygenation of clinically localized prostate cancer. METHODS AND MATERIALS: Intraprostatic oxygen tension was measured using the Eppendorf electrode in 55 unanesthetized men with localized prostate cancer before radiotherapy. Measurements were made along two tracks through regions of suspected tumor in the prostate, and core needle biopsies were then obtained from the same regions. RESULTS: The median pO(2) ranged from 0.2 to 57.3 mm Hg, and the grand median pO(2) was 4.5 mm Hg. The percentage of oxygen readings <5 mm Hg (HP(5)) ranged from 0% to 100% (median 60%). The track 1 oxygen readings were greater than those from track 2. Statistically significant heterogeneity was found in the individual oxygen readings: the between- and within-tumor components accounted for 32% and 68% of the total variability, respectively. However, the between-tumor variability in HP(5) significantly exceeded the within-tumor variability (61% vs. 39%). No association was found between oxygen values and clinical factors, including age, T stage, Gleason score, prostate-specific antigen level, hemoglobin concentration, or prior hormonal treatment. No difference was noted in the oxygenation between regions of tumor and normal prostate tissue, as determined from the core biopsies. CONCLUSION: Localized prostate cancer is characterized by marked hypoxia and significant heterogeneity in oxygenation, similar to other human tumors. The normal prostate may contain regions of low oxygen concentration. HP(5), as determined in this study, should adequately discriminate among patients with prostate cancer and allow the independent prognostic significance of oxygenation to be evaluated once the study matures.